Where does the theme of love first appear in Romeo and Juliet?
The theme of love is first established even before the play proper begins: in the prologue. A form of the word "love" appears twice in the prologue, in lines 6 and 9. The prologue also establishes that Romeo and Juliet's will not be a happy relationship; it calls their love "death-mark'd."
It is also interesting to note that the rivalry between the families of Capulet and Montague is introduced first, almost as if the grudge and civil warring is more important than the love plot.